This invention provides a semiconductor device having a field effect transistor comprising a gate electrode comprising a metal nitride layer and a polycrystalline silicon layer, and the gate electrode is excellent in thermal stability and realizes a desired work function. In the semiconductor device, a gate insulating film 6 on a silicon substrate 5 has a high-permittivity insulating film formed of a metal oxide, a metal silicate, a metal oxide introduced with nitrogen, or a metal silicate introduced with nitrogen, the gate electrode has a first metal nitride layer 7 provided on the gate insulating film 6 and containing Ti and N, a second metal nitride layer 8 containing Ti and N, and a polycrystalline silicon layer 9, in the first metal nitride layer 7, a molar ratio between Ti and N (N/Ti) is not less than 1.1, and a crystalline orientation X1 is 1.1